Apparatus with reduction/magnification image size processing for producing low-pass filtered images

Abstract

A circuit for filtering an input digital image comprising: first storage apparatus for storing the input digital image; apparatus for retrieving the input digital image from the first storage apparatus and generating a first resized digital image of reduced spatial frequency relative to the input digital image and being of smaller size than the input digital image; second storage apparatus for storing the first resized digital image; apparatus for retrieving the first resized digital image from the second storage apparatus and generating a second resized digital image of equal size to the input digital image, wherein the second resized digital image is a lowpass filtered version of the input digital image due to the reduced spatial frequency of the first resized digital image; and third storage apparatus for storing the second resized digital image.

I claim: 
     
       1. A video filtering system, comprising: a) input storage means for storing an input digital image;   b) first temporary storage means connected to said input storage means for temporarily storing said input digital image;   c) a first pair of series connected resizing apparatus connected to said input storage means for reducing said input digital image to a first reduced size and then magnifying said first reduced size digital input image to original size as a first low-pass filtered version of said input digital image;   c) a second pair of series connected resizing apparatus connected to said input storage means for reducing said input digital image to a second reduced size and then magnifying said second reduced size digital input image to original size as a second low-pass filtered version of said input digital image;   d) a multiplexer having a first input connected to said first temporary storage means, a second input connected to said first pair of series connected resizing apparatus, and a third input connected to said second pair of series connected resizing apparatus, for selecting said input digital image stored in said first temporary storage means for output on a first output thereof, and one of said first or second low-pass filtered versions of said input digital image on a second output thereof;   e) a first adder/subtracter connected to said first output and said second output of said multiplexer for adding or subtracting said selected one of said first or second low-pass filtered versions of said input digital image to or from said input digital image temporarily stored in said first temporary storage means and in response generating a first intermediate image;   f) a multiplier connected to said first adder/subtracter for multiplying said first intermediate image by a predetermined scaling factor and in response generating a second intermediate image;   g) a second temporary storage means connected to said first temporary storage means for further temporarily storing said input digital image;   h) a second adder/subtracter connected to said multiplier for adding or subtracting said second intermediate image to or from said input digital image temporarily stored in said second temporary storage means and in response generating an output filtered image.   
     
     
       2. The video filtering system of claim 1, wherein said input storage means comprises a frame store. 
     
     
       3. The video filtering system of claim 1 wherein said first and second temporary storage means are each comprised of a FIFO.